High voltage control arrangement



J n-11,1961 M. HICKEY Em 3,2 9,3

HIGH VOLTAGE CONTROL ARRANGEMENT Filed June 5, 1963 .28 ?0 32 33 iENERGY a? DETECTOR I I 40 38 .3 e DEFLECTION v GATING TRIGGER PULSE PuLsCIRCUIT GENERATOR GENERATOR FIG.

HIGH VOLTAGE REGULATED /42 POWER SUPPLY I I 'TO ACCELERATING ELECTRODE4a 100 v 54 o U.D.P. 2o TO L.D.P. 22

+eoov +1ooov -s|ov -|ov o 0 0 I .79 80 8| as as v +aoov -4|ov 92 -8OOV IL 78 L 66 llil|+ v gm y|m+- leoov 94 I6OOV 64 lsoov INVENTORS HQ 2 JOHNJ. HICKEY J- PfRRYJM/TH United States Patent 3,299,343 HIGH VOLTAGECONTROL ARRANGEMENT John J. Hickey and J Perry Smith, Hawthorne, Calif.,assignors, by mesne assignments, to TRW Inc., acorporation of Ohio FiledJune 3, 1963, Ser. No. 285,013 6 Claims. (Cl. 32323) This inventionrelates to high voltage control arrangements, and in particular tosimple and economical means for varying two or more high direct currentvoltages simultaneously without introducing excessive corona effects.

In certain electrical laboratory instruments which utilize relativelyhigh direct current potentials, such as oscillographs or electroniccameras, it is desirable to be able to vary two or more of thesepotentials.

One type of electronic camera system for photographing ultrahigh speedluminous transient phenomena employs an electrostatically operated imageconverter tube. The image converter tube serves both as a high speedelectronic shutter and as a means for amplifying the light image beingphotographed. The image converter tube comprises a photocathode forconverting the light image into a corresponding electron image, acontrol grid for gating the electron image, a generally cylindricalfocussing electrode for electrostatically focussing the electron imageonto a fluorescent screen, a conical accelerating electrode foraccelerating the electron image towardsthe fluorescent screen, and apair of electrostatic deflection plates for moving the electron imageacross the fluorescent screen.

In order to operate the camera in different modes it is necessary to beable to change the supply potentials of the deflection plates relativeto that of the accelerating electrode. For example, during initialfocussing and alignment procedures it is customary to apply'equalpotentials to the deflection plates and accelerating elect-rode. Forframing operation, in which three side by side images are obtained bythe application of properly timed voltage pulses to the deflectionplates and control grid, it is desirable to apply opposite and equalsupply voltages to the deflection plates relative to the acceleratingelectrode so that the first frame will appear off center on one side,the second frame centered, and the third frame oif center on theopposite side. For streak operation, in which a slit is imaged on thecenter of the photocathode and the resulting electron image then sweptacross the screen by applying'a linear ramp voltage to one or bothdeflection plates, the deflection plate supply voltages differ by agreater'amount than in framing operation in order that the image on thescreen will cover the same over-all picture area.

While it is possible to vary the high potentials on the deflectionplates relative to the accelerating electrode by switching the highvoltages directly from a common power supply, such practice causessevere corona problems. To avoid corona problems by employing separatepower supplies would entail extra cost.

Accordingly, it is an object of this invention to provide an arrangementfor altering two or more high direct current voltages applied from asingle source while minimizing corona effects.

A further object of the invention is to provide a simple and economicalmeans for oppositely varying two high potentials about a third fixedhigh potential.

The foregoing and other objects are achieved according to an embodimentof the invention in a control arrangement which includes a high voltagepower supply having two parallel branches in series therewith. Eachbranch includes a voltage regulator having an anode and a cathode and acurrent limiting resistor connected between the anode and the source. Avoltage divider network, which 3,299,343 Patented Jan. 17, 1967 mayconsist of two resistors is connected between the anodes of the voltageregulators. The cathodes of the voltage regulators are connected tovariable unidirectional voltages of much smaller magnitude than thesupply voltage. The variable voltages may be produced by means of aphase splitter. The phase splitter consists of a vacuum tube whose anodeis connected to the cathode of one of the voltage regulators and whosecathode is connected to the cathode of the other voltage regulator.Resistors of equal resistance value are connected in the anode andcathode circuits and to equal and opposite voltages.

The cathode circuit of the phase splitter operates like a cathodefollower in that a direct current voltage applied to the grid willproduce a corresponding voltage on the cathode of the same sign andnearly of the same magnitude. The voltage on the anode will be equal toand opposite that on the cathode since the anode current is equal to thecathode current. The appearance of these two voltages which aresubstantially smaller in magnitude than the supply voltage will bereflected by a corresponding change in the potentials on the anodes ofthe two voltage regulators. The anode potential on one regulator willincrease and the anode potential on the other regulator will decrease bythe same amount, while the potential at the midpoint of the voltagedivider network connecting these two anodes will remain constant.

In the drawing:

FIG. 1 is a schematic diagram of an electronic camera system in whichthe voltage control arrangement of the invention finds utility; and

FIG. 2 is a schematic circuit of one embodiment of the voltage controlarrangement according to the invention.

Referring now to the drawing, FIG. 1 is a schematic diagram of anelectronic camera system employing a voltage control arrangementaccording to the invention. The electroniccamera system includes as oneof its principal components an image converter tube 10 which functionsprimarily as a high speed shutter. Another function of the imageconverter tube 10 is that of providing light amplification for theextremely short frame times involved in its high speed photographicoperation.

The image converter tube 10 comprises essentially a cylindricalevacuated envelope 12 containing a photoemissive cathode or photocathode14 at one end, a fluorescent screen 16 at the other end, a control grid18adjacent to the photocathode 14, and a pair of deflection plates 20and 22 intermediate the control grid 18 and the fluorescent screen 16.Certain other parts and components essential to the operation of thetube 10 are omitted for simplicity, since these are well known. Forexample, the tube 10 ordinarily contains additional electrodes such asan anode and focussing electrodes and also requires a high voltagesupply. It will suffice to say that the tube may be one of the kindmanufactured by RCA and bearing the developmental type number C73435A.

In the operation of the electronic camera for the purpose ofphotographing high speed transient phenomena, light from an object 24 isfocussed by a lens 26 onto the photocathode 14 of the image convertertube 10. The electron image emitted from the photocathode 14 is normallyprevented from reaching the fluorescent screen 16 by the application ofsufliciently high negative blanking voltage to the control grid 18relative to the photocathode 14.

A rapid series of frames or exposures of the phenomenon or object 24 canbe taken by applying a series of positive rectangular gating voltagepulses to the control grid 18. The gating voltage pulses aresufliciently large, such as 300 volts, to unblank the grid 18 and permitthe electron image to be accelerated towards the fluorescent screen 16.The different frames or exposures may be reproduced side-by-side on thefluorescent screen 16 by applying deflection voltages to the deflectionplates 20 and 22 respectively, between and during successive gatingpulses. The amplified light images appearing on the fluorescent screen16 are then projected onto a photographic film 28 by means of a lenssystem 30. In practice, the film 28 may be part of a camera of the typewhich allows rapid development of the exposed film 28.

A gating signal for actuating the image converter tube is developed in acircuit which includes an electromagnetic energy detector 32 exposedthrough a lens system 34 to the phenomenon or object 24 to be recorded.The beginning of the event for example, may be manifested by the initialemission of light from the object 24. In such case, the detector 32 maycomprise a phototube circuit which converts the light into an electricalsignal. The electrical signal is fed to a trigger circuit 36 to developan amplified trigger pulse or a series of pulses of suflicient magnitudeto drive a gating pulse generator 38 and a deflection pulse generator 40which generate the desired gating and deflection pulses for operatingthe image converter tube.

For streak operation, a single gating pulse is applied to the controlgrid 18 while a linear ramp voltage is applied to one deflection plateor equal and opposite ramp voltages are applied to both deflectionplates. The scene is viewed through a slit that is orientedperpendicular to the direction in which the beam is swept so that thefilm records the trace left by the moving slit image.

As mentioned previously, it is necessary that the high voltage supplypotentials for the deflection plates 20 and 22 be varied for diflerentoperating conditions. Focussing and alignment procedures for the cameratube and lens systems are carried out with the deflection plates at thesame high positive potential. For framing operation, the supplypotentials on the deflection plates must be changed so that they diflerby one amount, while for streak operation the potentials are charged sothat they differ by another amount.

A circuit for varying the supply potentials on the deflection platesrelative to the anode is shown in FIG. 2. The positive side of a highvoltage power supply 42 is connected in series with two parallelbranches. One bran-ch includes a current limiting resistor 44 connectedto the anode of a high voltage regulator tube 46 and the other branchincludes a current limiting resistor 48 connected to the anode of a highvoltage regulator tube 50. A voltage divider consisting of two resistors52 and 54 of equal resistance value is connected between the anodes ofthe two regulator tubes 46 and S0. A vacuum amplifying tube 56, such asa triode, has its cathode connected at point 58 to the cathode ofvoltage regulator tube 46 and its anode connected at point 60 to thecathode of voltage regulator tube 50.

The cathode of the amplifying tube 56 is connected through a cathoderesistor 62 to a negative potential. The negative potential, which isvariable, is supplied from low voltage source 64 and voltage divider 66,the latter having a number of taps 68, 70, 72 from which a desiredvoltage can be selected through a selector switch 74.

The anode of amplifying tube 56 is connected through a plate resistor 76to a positive potential. Plate resistor 76 has the same resistance valueas cathode resistor 62. The positive potential, likewise variable, issupplied from a low voltage source 77 and voltage divider 78, the latterhaving a number of taps 79, 80, 81 selectable by a selector switch 82.

The control grid of the amplifying tube 56 is connected to a negativepotential through a switch 84 whichcan select one of a number of taps86, 88, 90 on a voltage divider 92 connected across a low voltage source94. v

The junction point 96 between resistors 44 and 52 and the anode ofvoltage regulator tube 46 is connected through a resistor 98 to thelower deflection plate 22 of the image converter tube 10.- The junctionpoint 100 between resistors 48 and 54 and the anode of voltage regulatortube 50 is connected through a resistor 102 to the upper deflectionplate 20 of the image converter tube 10. The junction point 104 betweenthe two resistors 52 and 54 is connected to the accelerating electrodeof the image converter tube 10.

In accordance with one preferred set of conditions for operating theimage converter camera system a voltage of 20 kilovolts is supplied tothe parallel branches by the high voltage power supply42. The voltageregulator tubes 46 and 50 regulate the voltage across their electrodeswithin 2% of 15 kilovolts over a range of 5 00 microamperes. Switch 82connects plate resistor 76 to a positive potential of 800 volts on tap80, and switch 74 connects cathode resistor 62 to a negative potentialof 800 volts on tap 70. For focussing and alignment, switch 84 connectsthe grid of amplifier tube 56 to a potential of about 10 volts on tap90,

Tube 56 is connected as a phase splitter, which produces substantiallyequal and opposite voltages at, the cathode and anode (points 58 and60), with the cathode following the voltage applied to the grid.However, the cathode voltage will always be slightly positive withrespect to the grid unless grid current is drawn. Also the minimum anodepotential will always be positive relative to the cathode by amount, forexample 20 volts. Thus, when'the grid voltage is about l0 volts, thepotential of point 58 will be 10 volts negative and the potential ofpoint 60 will be 10 volts positive. The potential of point 96 is 15kilovolts positive relative to point 58 and thus will be 14,990 volts.The potential of point 100 is 15 kilovolts positive. relative to point60 and thus will be 15,010 volts. Point 104, which is at a potentialmidway between points 96 and 100, will be at 15 kilovolts. Thus, forpractical purposes points 96, 100, and 104 are essentially at the samepotential of 15 kilovolts.

For framing operation switch 84 is moved to tap 88 to connect the gridof tube 56 to a negative 410 volts. Since the cathode circuit of tube 56operates like a cathode follower, the grid voltage will be substantiallyreproduced on the cathode, thereby placing point 58 at 400 voltsnegative. Since the same tube current flows through plate and cathoderesistors 76 and 62 the drops across the equal resistances are equal,thereby placing point 60 at 400 volts positive. Point 96 is 15 kilovoltsabove point 58, and point 100 is 15 kilovolts above point 60. Thus,point 96 will connect about 14.6 kilovolts to the lower deflection plateand point 100 will connect about 15.4 kilovolts to the upper deflectionplate. Point 104 remains fixed at 15 kilovolts, which is supplied to theaccelerating electrode.

For streak operation, switch 84 is moved to tap 86 to connect the gridof tube 56 to a negative 610 volts. The voltage at point 58 now becomes600 voltsnegative and point 60 becomes about 600 volts positive. Point96 becomes 14.4 kilovolts and point 100 becomes 15.6 kilovolts. Point104 remains at 15 kilovolts.

So long as equal and opposite voltages are at points 58 and 60, thepotential at point 104 will remain fixed midway between the potentialsat points 96 and 100. However, it is possible to switch the voltage atpoint 104 by making the voltages at points 58 and 60 unequal. Forexample, if switch 74 is moved to tap 68, which is 1000 volts negative,and switch 82 remains at 800 volts positive, then a grid voltage of 610volts negative will produce a voltage of 600 volts negative at point 58,or a voltage drop of 400 volts across the cathode resistor 62.Since'there must be a 400 volt drop across the plate resistor 76 also,point 60 must be at 400 volts. Point 96 Will be at 14.4 kilovolts andpoint 100 will be at 15.4 kilovolts, there by placing point 104 at 14.9kilovolts or 100 volts less than it was originally. An analogous ge involtage at point 104 can be brought about by changing the voltageapplied to the anode by source 77 through switch 82.

It will now be appreciated that the grid of tube 56 can be switched byrelatively low voltages to produce changes in the high voltagesfurnished by the high voltage supply 42. A single low voltage on thegrid is effective to produce changes in the two voltages applied to thedeflection plates. Furthermore, a change in either the cathode or platesupply voltage will produce a change in the voltage (at point 104)supplied to accelerating anode. Thus, by reducing the number ofcomponents opearting at high potentials there has been a reduction incorona problems. In accordance with one operative embodiment thefollowing circuit values and components were used:

Resistors 44, 48 megohms each 30 Resistors 52, 54 do 20 Tube 56 Type 12AT7 Resistors 62, 76 kilohms each 200 Resistors 98, 102 megohms each 10The regulators 46 and 50 were type Ml08-15 Corotron voltage regulatorsmanufactured by Victoreen Instrument Co. of Cleveland, Ohio.

The embodiments of the invention in which an exclusive property orprivilege is claimed as defined as follows:

We claim:

1. A high voltage control arrangement, comprising:

a source of relatively high unidirectional supply volt age;

a pair of parallel branches in series with said source,

each branch including a voltage regulator and a current limitingresistor connected between said source and the anode of said voltageregulator;

a voltage divider network connected between the anodes of said voltageregulators;

and means connecting the cathodes of said voltage regulators to variableunidirectional control voltages of substantially smaller magnitude thansaid supply voltage.

6 2. The invention according to claim 1 in which said last mentionedmeans includes a phase-splitting network whose outputs are coupled tosaid cathodes.

3. A high voltage control arrangement, comprising:

a source of relatively high unidirectional supply voltage;

a pair of parallel branches in series with said source,

each branch including a voltage regulator and a current limitingresistor connected between said source and the anode of said voltageregulator;

a voltage divider network connected between the anodes of said voltageregulators;

a vacuum tube having a cathode, a control grid, and an anode, with thecathode and anode connected across the cathodes of said voltageregulators;

two resistors connected in the anode and cathode circuit respectively ofsaid vacuum tube;

means for applying operating potentials to that cathode and anode ofsaid vacuum tube;

and means for selectively applying various potentials to said grid thatare of substantially smaller magnitude than said supply voltage, therebyaltering the potentials on the anodes of said regulators.

4. The invention according to claim 3, wherein the resistors in saidanode and cathode circuit are of equal value and the supply voltages forsaid cathode and anode are equal and opposite in polarity.

5. The invention according to claim 3 and further including a connectionto the mid-potential point of said voltage divider-network.

6. The invention according to claim 5 and further including means forselectively applying diiferent operating potentials to the anode andcathode of said vacuum tube, thereby altering the potential of saidmid-potential point.

No references cited.

JOHN F. COUCH, Primary Examiner.

K. D. MOORE, Assistant Examiner.

3. A HIGH VOLTAGE CONTROL ARRANGEMENT, COMPRISING: A SOURCE OFRELATIVELY HIGH UNIDIRECTIONAL SUPPLY VOLTAGE; A PAIR OF PARALLELBRANCHES IN SERIES WITH SAID SOURCE, EACH BRANCH INCLUDING A VOLTAGEREGULATOR AND A CURRENT LIMITING RESISTOR CONNECTED BETWEEN SAID SOURCEAND THE ANODE OF SAID VOLTAGE REGULATOR; A VOLTAGE DIVIDER NETWORKCONNECTED BETWEEN THE ANODES OF SAID VOLTAGE REGULATORS; A VACUUM TUBEHAVING A CATHODE, A CONTROL GRID, AND AN ANODE, WITH THE CATHODE ANDANODE CONNECTED ACROSS THE CATHODES OF SAID VOLTAGE REGULATORS; TWORESISTORS CONNECTED IN THE ANODE AND CATHODE CIRCUIT RESPECTIVELY OFSAID VACUUM TUBE; MEANS FOR APPLYING OPERATING POTENTIALS TO THATCATHODE AND ANODE OF SAID VACUUM TUBE; AND MEANS FOR SELECTIVELYAPPLYING VARIOUS POTENTIALS TO SAID GRID THAT ARE OF SUBSTANTIALLYSMALLER MAGNITUDE THAN SAID SUPPLY VOLTAGE, THEREBY ALTERING THEPOTENTIALS ON THE ANODES OF SAID REGULATORS.